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Abstract

Background:

Medial malleolus fractures (MMFs) are common across the world. Currently, there is a lack of consensus on the number of screws used in fixation of MMF. Our aim was to compare the radiographic outcomes of MMF with patients between fractures that have either undergone single-screw (SS) or dual-screw (DS) fixation.

Methods:

This retrospective study assessed patients who had undergone fixation of their MMF from 2012 to 2022. Analysis of their perioperative radiographs was performed to determine the initial type of injury and then radiographic outcomes of nonunion and malunion.

Results:

A total of 653 patients suffering bimalleolar fractures were identified across a 10-year period. There were 271 patients (41.50%) in the SS group and 382 in the DS group (58.50%). There was no difference found in the nonunion rate of SS (19.19% [52 of 271]) compared with DS (18.85% [72 of 382]) (P = .931). A statistically significant difference between malunion rates was found between the SS group (11.07% [30 of 271]) compared with the DS group (3.93% [15 of 382]) (P < .001).

On multiregression analysis, factors that gained significance for development of nonunion was nonfixation of syndesmosis (P = .039), ankle dislocation on arrival (P < .001), and nonrestoration of fibular length (P < .001). Other factors that showed significance for failure to achieve medial anatomical reduction was nonfixation of syndesmosis (P < .001).

Conclusion:

Use of an SS rather than DS showed a significant increase in nonanatomical reduction but did not increase nonunion or reoperation rate. Syndesmosis fixation was associated with higher rates of MMF nonunion and malunion; as such, surgeons should have a low index of suspicion of injury and fixation.

Level of Evidence:

Level III, retrospective case series.

Keywords

medial malleolus ankle fracture medial malleolus outcomes

Introduction

Medial malleolus fractures (MMFs) are common injuries presenting to an orthopaedic trauma practice. They can occur in isolation or most commonly in combination with lateral or posterior malleolus fractures. The prevalence of MMF has been found to reach up to 45%.^2,10 Over a 10-year period within the United Kingdom, Scott et al¹⁸ identified almost 250 000 hospital admissions due to an ankle fracture. Of these admissions, approximately 60% were bimalleolar or trimalleolar injuries, with around 11% being solitary MMFs.¹⁸ The high prevalence of ankle fractures and specifically MMFs result in a large economic burden.²⁰

There is no clear consensus on methods of osteosynthesis of MMF. Lampridis et al¹¹ identified in their review of factors affecting stability in ankle fracture that medial column (deltoid ligament) integrity is of key importance when considering stability in ankle fractures. Currently, practices for MMF management include nonoperative management or commonly operative treatment with tension band wiring, screw fixation, or plate fixation, depending on fracture size and orientation.⁴ Verhage et al²¹ found that isolated MMFs had worse clinical outcome scores on American Academy of Orthopaedic Surgeons (AAOS) and American Orthopaedic Foot & Ankle Society (AOFAS) scores as compared to isolated fibula and combined fibula and posterior malleolus fractures. Hu et al⁹ found that adverse radiographic outcomes (delayed or nonunion, malunion) were significantly associated with worse ankle function and higher incidence of posttraumatic osteoarthritis. Adequate anatomical reduction has been found to be a significant contributing factor in better outcomes for patients.^9,21

There are few studies in the literature that review the outcomes of single-screw (SS) compared with dual-screw (DS) fixation for MMF. The primary aim of this study was to analyze the difference in radiographic outcomes of DS and SS fixation of MMF, specifically, examining nonunion and malunion rates with the null hypothesis that there is no difference between the two groups.

Methods

This was a retrospective observational study of all patients who were admitted for surgical fixation of a bimalleolar or trimalleolar ankle fracture to a level 1 major trauma center between August 2012 and August 2022. Data were obtained from our institution’s prospective electronic patient record system (Bluespier, Droitwich, UK). Inclusion criteria were all adult patients who had sustained an ankle fracture that included an MMF that had undergone open reduction and internal fixation. Patients with isolated MMF, because of a lack of sufficient case load, and those who did not have follow-up radiographs were excluded. Pilon fractures were not included in the cohort.

Ankle fracture characteristics were analyzed on our Picture Archiving and Communication System (Carestream Health Inc, New York). Analysis was performed of all preoperative, intraoperative, and postoperative imaging. Data collected included demographics of the patients, soft tissue injury, and dislocation of the ankle joint. Lauge-Hansen classification was used for the ankle fractures with further classification of MMF according to Herscovici.⁸ The method of fixation, number of screws used, type of screws, and if screws were parallel or not was recorded.^8,12
-16

Postoperative imaging was analyzed, and all patients’ most recent postoperative imaging was used to determine whether there was any radiologic evidence of nonunion, union, or malunion of the MMF. Malunion was defined as displacement on at least 1 radiograph >1 mm. Nonunion was defined as no trabecular crossing on at least 2 radiographs at least 9 months postsurgery. Finally, electronic patient records were assessed whether patients underwent a reoperation and what was the indication.

Statistics

Statistical analysis was performed using SPSS (IBM Corp, Armonk, NY). Comparisons were made between group characteristics. χ² and Fisher exact tests were used for categorical variables and independent samples t tests and Mann-Whitney U test for variable means. Uni- and multivariate analyses were performed using univariate and multivariate logistic regression analysis to identify factors affecting nonunion and malunion rates. Any factor that achieved significance on univariate analysis underwent further multivariant regression analysis. Variables were determined as those relating to objective and measurable factors relevant to fracture reduction and fixation methods. Significance was given to variables that reached P < .05.

Results

Demographics

A total of 653 patients were identified across a 10-year period that could be included in the study. There were 271 patients (41.50%) in the SS group and 382 patients in the DS group (58.50%). The average age of patients was 47.7 years (95% CI 46.33, 49.14). Thirty-seven patients (5.6%) sustained an open ankle fracture. Acute ankle dislocation was evidenced on initial radiographs at presentation in 45% (293 of 653) of patients. (Dislocation was defined as ≥50% subluxation of the tibiotalar joint on any radiographic view.) When assessing the fracture pattern in MMFs, almost 50% (323 of 653) of cases were classified as type C according to Herscovici. The number of screws used differed across the Herscovici classification (Table 1), with higher rates of single screws used in types A and B. This difference was significant (P < .001). Most fractures were supination external rotation fracture types (494 of 653) (Table 1). There was no significant difference in the number of screws used across the Lauge-Hansen fracture classification (Table 1, P = .499).

Table 1.

Crosstabulation of Herscovici Classification and Lauge Hansen Classification With Number of Screws Used for Medial Malleolar Fixation.

		^{One Screw, n (%)}	^{Two Screws, n (%)}	Total
Herscovici Classification	A	25 (78.10)	7 (21.90)	32
	B	95 (54.30)	80 (45.70)	175
	C	106 (32.80)	217 (67.20)	323
	D	44 (37)	75 (63.00)	119
	Total	270 (41.6)	379 (58.40)	649
Lauge Hansen	SAD	16 (41.00)	23 (59.00)	39
	SER	198 (40.10)	296 (59.90)	494
	PER	40 (47.60)	44 (52.40)	84
	PAB	16 (48.50)	17 (51.50)	33
	Total	270 (41.50)	380 (58.50)	650

Abbreviations: PAB, pronation abduction; PER, pronation external rotation; SAD, supination adduction; SER, supination external rotation.

The overall nonunion rate for ankle fractures was 19.00% (124 of 653) (Table 2). The difference between the 2 groups was not statistically significant (P = .913). The overall malunion rate was 6.90% (45 of 653) This difference was statistically significant (P < .001) (Table 2). The overall reoperation rate was 12.90% (84 of 653). Reoperation rates were identified within the 2 groups. SS fixation displayed a reoperation rate of 14.76% (40 of 271), and DS fixation had a reoperation rate of 13.02% (44 of 382). There was no significant difference found between DS and SS when assessing rates of reoperation (P = .237).

Table 2.

Crosstabulation of Radiographic Bone Union and Anatomic Reduction With Number of Screws Used for Medial Malleolar Fixation.

	No, n (%)	Yes, n (%)	Total	P Value
Union
1 screw	52 (19.2)	219 (80.8)	271	.913
2 screws	72 (18.8)	310 (81.2)	382
Total	124 (19)	529 (81)	653
Anatomic reduction
1 screw	30 (11.1)	241 (88.9)	271	<.001
2 screws	15 (3.9)	367 (96.1)	382
Total	45 (6.9)	608 (93.1)	653

Further analysis of the whole cohort identified factors that could possibly contribute to the development of nonunion. When assessing nominal variables for nonunion, an initial univariate and then multivariate regression analysis was performed for nonunion (Table 3) and malunion (Table 4). For nonunion, both anatomic reduction, fibular length restoration, and initial ankle fracture dislocation were significant factors that contributed significantly (P < .001, respectively). For malunion, the use of 1 as compared to 2 screws and achievement of bone union were significant factors in the development of malunion (P = .009).

Table 3.

Multivariate Regression Analysis of Factors That May Contribute to the Development of Nonunion in Medial Malleolus Fractures.^a

		Univariate				Multivariate
				95% CI				95% CI
		P Value	Odds Ratio	Lower	Upper	P Value	Odds Ratio	Lower	Upper
Percutaneous/open		.202	0.516	0.186	1.428
Open fracture		.671	0.839	0.374	1.884
Ankle dislocation		<.001	0.386	0.257	0.578	<.001	0.412	0.27	0.627
One or 2 screws		.913	1.022	0.688	1.52
Screw thread		.642	1.112	0.71	1.743
Anatomic reduction		.004	2.559	1.343	4.877	.005	2.670	1.340	5.321
Parallel screws
	Anteroposterior	.336	0.822	0.552	1.225
	Lateral	.887	0.979	0.727	1.318
Syndesmosis fixation		.03	0.641	0.429	0.959	.073	0.675	0.44	1.037
Fibular length not restored		<.001	4.509	2.747	7.402	<.001	4.323	2.583	7.236

Boldface indicates significance (P < .05).

Table 4.

Multivariate regression analysis of factors which contribute to the development of malunion in medial malleolus fractures.^a

		Univariate				Multivariate
				95% CI				95% CI
		P Value	Odds Ratio	Lower	Upper	P Value	Odds Ratio	Lower	Upper
Percutaneous/open		.136	3.723	0.661	20.966
Open fracture		.336	0.587	0.198	1.738
Ankle dislocation		.794	0.922	0.503	1.693
1 or 2 screws		.001	3.046	1.605	5.78	.009	2.533	1.262	5.084
Screw thread		.004	2.466	1.325	4.589	.115	1.732	0.875	3.425
Bone union		.004	2.559	1.343	4.877	.003	2.839	1.438	5.605
Parallel screws
	Anteroposterior	.37	1.347	0.702	2.586
	Lateral	.091	1.823	0.908	3.66
Syndesmosis fixation		.044	0.534	0.29	0.983	.308	0.589	0.213	1.629
Fibular length not restored		.809	0.888	0.34	2.321

Boldface indicates significance (P < .05).

Discussion

We found no significant difference in nonunion rates or reoperation rates when comparing SS and DS fixation. However, there was a significant difference regarding malunion rate, with a higher malunion rate in the SS group (OR 2.533, 95% CI 1.262, 5.084). We identified that nonrestoration of fibular length contributed to the development of nonunion.

Our comparison of SS with DS fixation displayed no significant difference in nonunion rates across a 10-year period. This is similar in the literature, although nonunion rates vary significantly. Mandel et al¹⁷ found no significant difference between nonunion rates of SS and DS groups (1.9% vs 0%, P = .259) in their retrospective analysis of 196 patients at a 1-year follow-up assessment. These findings were mirrored by Shah et al.¹⁹ Buckley et al¹ did not find any difference in the nonunion rates of SS and DS fixation groups with 24 months of postoperative follow-up.

The nonunion rates in the current article appear to be higher than previously reported in studies comparing SS and DS fixation for MMF. Our study was the largest cohort size to date with a long-term follow-up to a maximum of 10 years; however, we have used radiographs to identify nonunion. Our study may therefore overestimate numbers of nonunions as compared to other studies that use CT for diagnosis. Other studies have suggested that DS fixation of MMF is superior. An 8-year retrospective analysis performed by Cheng et al⁶ found that DS fixation resulted in a significantly lower rate of nonunion (3% vs 22%, P = .0032) of MMF. The authors hypothesized that rotational stability with the second screw may be the contributing factor to why nonunion was more common in the SS group.⁶ Further to this, reoperation rates were not significantly different between the SS and DS groups, which is in keeping with the current literature.^1,17

Our analysis identified that malunion rates were significantly lower in the DS group. Currently, there is little evidence assessing the malunion rates within the DS and SS groups. Hu et al⁹ assessed factors affecting poor radiographic outcomes in MMFs, and it was found that fair (>1 mm intraarticular gap) or poor (>2 mm intraarticular gap) union was significantly associated with poorer radiographic outcomes (P < .001)Those patients who displayed poorer radiographic outcomes were also associated with significantly worse patient-related outcome measures (P < .001).⁹ Buckley et al¹ found that an increasing number of malreduction factors in an ankle fracture was significantly associated with poorer functional outcomes. It has been postulated that SS is being used in groups that present with smaller MMF fragments (Herscovici types A and B) and as such are more difficult to obtain anatomical reduction compared with the DS group.^1,17,22

Further assessment of the whole cohort with a multiregression analysis identified factors affecting nonunion of MMFs. Obtaining an anatomical reduction and restoration of fibular length was significantly linked with achieving union. This may be due to the inability to obtain primary bone healing because of the presence of a gap resulting from an increase in the forces applied to the medial malleolus due to malreduction. Fibular length restoration would increase the traction force on the medial malleolus as the hindfoot propagates laterally. Biomechanically, studies have already reviewed the amount of stiffness and maximum load in SS fixation compared with DS and Giordano et al⁷ found no significant difference in their biomechanical study. Ankle fracture dislocation was identified to be significantly associated with MMF nonunion. It is commonly regarded that the medial periosteum can be caught in the fracture. Theoretically, with an ankle fracture dislocation, the major initial displacement may give rise to the entrapped periosteum.⁴

On review of the literature assessing outcomes for ankle fractures, it was found that open fractures (P = .018) and overweight patients (P = .03) were significantly associated with nonunion.³ Although patient-specific morbidities were not assessed in this study, fracture-related factors such as open fracture or dislocation were not associated with malunion or nonunion. Additionally, recent evidence has found that adequately reduced MMFs following fibula fixation do not provide any significant improvements in function when fixed than when left to heal.⁵

There are limitations in the current study. The retrospective nature of the study resulted in gaps within our analysis, particularly pertaining to follow-up radiographs, because several patients were excluded from the review because of a lack of follow-up imaging. Additionally, because of a lack of access to intraoperative imaging, loss of reduction following MMF fixation was not specifically assessed. There were also no patient-reported outcomes collected; as such, we have not compared radiographic outcomes to patient functional outcomes. Additionally, although nonunion and malunion definitions were clearly defined, there may be an element of subjectivity on assessment of these images. Nevertheless, this was the largest MMF study analyzing nonunion and malunion to date.

Conclusion

Overall, our retrospective review identified that there was no significant difference in the nonunion rate between DS and SS fixation of MMFs. Despite this finding, malreduction rates were significantly higher in the SS cohort. This may be due to the prevalence of a smaller MMF fragment in this group (Herscovici A and B), which is more difficult to reduce. Nonrestoration of fibula length and ankle dislocation on admission were significantly associated with an increased risk of nonunion.

Supplemental Material

sj-pdf-1-fao-10.1177_24730114241291064 – Supplemental material for A Retrospective Case Series of Single-Screw vs Dual-Screw Fixation for Treatment of Medial Malleolus Fractures

Supplemental material, sj-pdf-1-fao-10.1177_24730114241291064 for A Retrospective Case Series of Single-Screw vs Dual-Screw Fixation for Treatment of Medial Malleolus Fractures by Junaid Aamir, Robyn Caldwell, Sarah Long, Sachith Sreenivasan, Jason Mavrotas, Ayn Panesa, Shagilan Jeevaresan, Vasileios Lampridis and Lyndon Mason in Foot & Ankle Orthopaedics

Footnotes

Ethical Approval

Our institutional review board judged the study to be a service provision project and therefore no formal ethics approval was required. All human studies have been approved by the appropriate ethics committee and have therefore been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments. National laws have been adhered to.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. Disclosure forms for all authors are available online.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Informed consent

Patients were retrospectively analyzed. No consent required.

ORCID iDs

Junaid Aamir, MBChB, MRes, MRCS,

Sachith Sreenivasan, MBChB, MRCS,

Vasileios Lampridis, MD, MSc, PhD, FRCS(Tr&Orth), FEBOT,

Lyndon William Mason, MBBCh, MRCS, FRCS(Tr&Orth), FRCS,

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